Compute index lazily
Compute index lazily

No need to precompute it.

//cc @josh

deckar01/task_list,deckar01/task_list,github/task_list,krayinc/task_list,seem-sky/task_list,krayinc/task_list,seem-sky/task_list,codydaig/task_list,github/task_list,codydaig/task_list,deckar01/task_list,deckar01/task_list,codydaig/task_list,krayinc/task_list,github/task_list